1. Field of the Invention
The present invention relates to ink jet or bubble jet printing by which an image is formed through ejection of ink droplets from the nozzles of plural print elements on a print head, and more particularly to ensuring that the print elements do not become clogged and ensuring that the free flow of ink through such nozzles is maintained.
2. Description of the Related Art
In conventional ink jet or bubble jet printing (collectively, "ink jet"), an image is formed by ejection of ink in droplets formed through piezoelectric or resistance heating through a plurality of fine nozzles. As is known, and due to the fineness of such nozzles, it is easy for the nozzles to become clogged, thereby restricting the flow of ink therethrough and adversely affecting the print quality. As a consequence, various techniques are known for preventing clogging of the nozzles. Such techniques include capping of the nozzle during quiescent periods of the printer (i.e., in the absence of a printing operation), purging ink from the nozzle by applying suction to the nozzle so as to draw ink out through all such nozzles, and wiping the face of the print head containing such nozzles so as to remove back-scattered ink and paper particles and residual dried ink and debris.
Generally speaking, mechanisms for performing such unclogging and clogging-preventative operations are disposed at extreme left- or right-ends of a printing platen against which the print head operates. Accordingly, conventional ink jet printers will have a capping/purging station at a left-most edge of a printing platen, at an area which will not be blocked while a recording medium (such as a paper sheet) is on the platen. During a printing process, the printing head will periodically be moved to the capping/purging station to purge the nozzles by suction, so as to ensure that the print elements do not become clogged.
Recently, it has become increasingly popular to print on a larger variety of recording mediums, such as large-format A-3 size paper, T-shirt transfer materials, and the like. At the same time, it is also desirable to decrease the overall "footprint" of the printer, i.e., to decrease the size of the printer itself. However, since the capping/purging station must be located outside the path of the recording medium, increasing the size of recording mediums has necessarily caused an increase in size of the printer.
Recently, it has been proposed to dispose the capping/purging station beneath the feed path of the recording medium, so as to decrease the footprint of the printer. However, since the capping/purging station is beneath the recording medium during a printing operation, it is not possible to perform capping or purging operations during recording. To prevent clogging in such an arrangement, an ink collection station is disposed at the edge of and outside of the recording medium feed path, and the print head is periodically moved to the collection station where all ink nozzles are fired so as to ensure that they do not become clogged. Since the waste collection stations are smaller in size than a capping/purging mechanism, this arrangement results in a small reduction in size relative to printers having a capping/purging station at the edge of the recording medium path.
However, further reductions in size are desirable. In addition, the periodic movements of the print head to the waste collection station results in an increased printing time which is also not desirable.